A guest at the San Ysidro Ranch in Montecito, Calif., says Pattinson, 27, and Perry, 28, were spotted scoping out a wedding rehearsal of two strangers on Sunday afternoon.

"Katy and Rob were just sitting next to each other watching the wedding rehearsal in the main courtyard area," rehearsal guest Stephanie Sands tells PEOPLE. She says her friend, the bride, spotted them. "They were dressed very casually. She was wearing a hoodie and big sunglasses. There was no PDA between them and no body language that showed they were dating. They just sat together and watched."

Sands says she has "no idea" why the pair – longtime friends and both now notably single – were at the location or why they were checking out the rehearsal, insisting, "They were not affiliated with the wedding party and were not seen mingling with guests." Another person who claimed to be a guest tweeted that the pair seemed to be with a group of a few other people.

Another source says Perry was spotted driving from L.A. to the luxury hotel, not far from her parents' home in Santa Barbara, before the weekend. Reps would not comment.